1) a payment in addition to what is usual, necessary or expected, e.g. and extra payment to workers (bonus)

2) (of a word) to suggest (something) in addition to its basic meaning (connote)

3) a person who has a share in the profits of a business etc in addition to her or his salary or wages (co-partner)

4) a gift (of money in addition to pay or a pension) to a retiring employee for her or his activity (gratuity)

5) advantages, such as a car, money in the form of paid expenses etc, given in addition to salary (perks)

6) a type of goods sold in addition to the main goods; an occupation which is not one's main work (sideline)

7) a payment demanded in addition to the usual charge, e.g. for a letter without enough postage paid on it (surcharge)